1. Field of the Invention
The present invention relates to a ratchet-type ring spanner and, more particularly, to an improved ring spanner which is particularly useful for repairmen.
2. Description of the Related Art
Hand tools play a role in a civilized society, and spanners are the most important one in the field of hand tools since the invention of the bolts and nuts. A wide variety of spanners have been available heretofore, such as combination wrenches, open wrenches, ring spanners, socket ratchet wrenches, etc. FIG. 6 of the drawings illustrates a socket ratchet wrench which includes a handle 40 and a switch button 41 mounted in a head portion 42 thereof to change a reversible direction of a ratchet mounted in the head portion 42 during operation. A drawback of the socket ratchet wrench is that a user has to hold the socket ratchet wrench with one hand and switch the switch button 41 when changing the reversible direction. A further drawback of the socket ratchet wrench is that it has a relatively large end in order to accommodate complex elements therein, and thus cannot be used in a limited space as additional sockets have to be used.
A professional repairman would use a combination wrench (see FIG. 7 of the drawing), open wrenches or ring spanners in a limited space for tightening or loosening of nuts. Yet a common drawback of these spanners/wrenches is that, after being rotated through a small angle, the spanner/wrench has to be removed from the nut and re-engaged with the nut for being rotated through another small angle. This process continues until tightening or loosening of the nut is accomplished, which is very inconvenient, especially in a limited space.
A reversible ring spanner has been proposed to solve the above-mentioned drawbacks, such spanner includes a ratchet wheel mounted in an inner periphery of a head portion thereof and a cavity defined in a web area thereof for receiving a spring and a pawl therein. The pawl is biased by the spring to engage with and disengage from the ratchet wheel to provide the required reversible function. It is, however, found that, as the pawl merely engages with one tooth of the ratchet wheel, the obtained torque is relatively small, and the pawl may be damaged if a relatively large force is applied. In addition, it is very difficult to provide a cavity in the web area of the spanner with a thickness of one (1) centimeter. Furthermore, the cavity must extend in an oblique manner in order to assure proper engagement between the ratchet wheel and the pawl, which further increases the difficulty of provision of the cavity as the tolerable error is extremely small. Although the problem can be solved by increasing the thickness of the head of the spanner, yet the enlarged head, like those of socket ratchet wrenches, would not allow the spanner to be operated in a limited space.
Therefore, there has been a long and unfulfilled need for an improved ratchet-type ring spanner to mitigate and/or obviate the above problems.